On November 11, 1918, at 11 am, World War I, the so-called Great War, officially came to a close. Over 10 million had perished, 21 million had been injured, and 7.7 million remained missing or imprisoned.

A year later, as the world began to catch its collective breath, the occasion was commemorated by the first Armistice Day. In 1920, unidentified casualties from the conflict were interred at Westminster Abbey in London, and the Arc de Triomphe in Paris in symbolic recognition of those who had sacrificed their lives. A similar ceremony was held at Arlington National Cemetery in Arlington,Virginia, in 1921; Italy, Belgium, Portugal, and Romania also honored anonymous victims of the conflict that year. Then known as Armistice Day, November 11 did not become a national holiday in the U.S. until 1938, just as the European powers were on the verge of sparking another worldwide conflagration, World War II.

In the wake of the horrors of this second cataclysm, Armistice Day was adapted to honor the veterans of that conflict as well. In the United States, following the Korean War, it became Veterans Day in 1954. The holiday honored veterans of all U.S. wars. The United Kingdom eventually chose the second Sunday of November (Remembrance Sunday) to honor its veterans, though it retained Armistice Day to specifically recognize World War I and II veterans, as did Canada, France, and Australia.

In the United States an official ceremony attended by the president (or a designee) is held on the 11th of November at the Tomb of the Unknowns. The queen of England, accompanied by the Royal Family, the prime minister, and other members of the government, conducts a similar ceremony at the Cenotaph at Whitehall on the second Sunday of the month.

Smaller local ceremonies are typically held nationwide in observant countries, with parades attended by resident veterans dressed in their military finery.

At 11 am, many observe two minutes of silence.

That tradition was the inspiration for a recent charity single released by Radiohead frontman Thom Yorke. The ‘song,’ which features an array of celebrities, is essentially ambient noise; it is accompanied by a video depicting the participants standing in respectful silence.